Coordinated and integrated signals between the hypothalamus, the pituitary and the gonads are necessary for successful mammalian sexual maturation and reproduction. Gonadotropin-releasing hormone (GnRH), a hypothalamic decapeptide, is central to the initiation and control of this reproductive hormone cascade. The importance of GnRH in this regulatory pathway is illustrated by the hypogonadal, GnRHdeficient hpg mouse, which have a deletion within the GnRH gene. These mice provide a useful model system that can be studied to better understand GnRH neuronal function and neuroendocrine regulation of GnRH production and release. One potential avenue for rescue of reproductive integrity of the hpg mice is to use a viral vector system to deliver the intact GnRH gene to GnRH neurons in these mice. The challenge of gene therapy to the nervous system is to develop nontoxic vectors that can achieve stable transgene expression in post-mitotic cells. The HSV amplicon vector is a unique vector that has high DNA capacity, is highly infectious to cells of the nervous system in rodents and humans, has essentially no toxicity when packaged free of helper virus, and theoretically can achieve stable and prolonged expression of the delivered gene. Delivery of the GnRH gene to neurons in the hypothalamus of the hpg mouse and evaluation of subsequent GnRH expression and reproductive function can serve as a tool to evaluate the success of the HSV amplicon for gene therapy to the nervous system. The overall goal of this project is to use the HSV amplicon viral vector system to deliver the gonadotropin-releasing hormone (GnRH) gene to GnRH neurons in hypogonadal, GnRH-deficient hpg adult female mice. The Specific Aims of this proposal are: (1) to determine whether prolonged, regulated expression of GnRH can be achieved in hpg adult female mice injected with HSV, GnRH amplicon; and (2) to characterize the reproductive function of hpg mice after gene delivery This experimental system will serve as a model to help us attain two specific objectives: (1) to assess the utility of the HSV amplicon for prolonged gene replacement therapy in the treatment of central nervous system (CNS) neuronal disorders; and (2) to better understand the physiology of hypothalamic GnRH action and regulation in vivo. [unreadable] [unreadable]